Burying underwater pipelines in fluidified inert material is known from documents U.S. Pat. No. 4,352,590, PCT Patent Application No. WO 2005/005736, PCT Patent Application No. WO 2009/141409, U.S. Pat. No. 4,992,000, U.S. Pat. No. 4,334,801, U.S. Pat. No. 4,400,115 and U.S. Pat. No. 5,659,983. In WO 2009/141409, the pipeline is buried by fluidifying a tilled portion of the bed of the body of water underneath the pipeline. Though effective, this method has the drawback of dispersing particles of inert material in the water. Fluidifying the inert material causes the pipeline to sink into the bed of the body of water, but tilling the bed and forced fluidification in situ of the tilled inert material produce minute particles of inert material that take a long time to settle, and so pose various problems: poor coverage of the pipeline, resulting in a depression along the trench; and dispersion of inert material in the pipeline area, thus contaminating flora and fauna. If caught and transported by water currents, the inert material particles in the pipeline area may even be carried relatively long distances. In documents PCT Patent Application No. WO 2009/141409, U.S. Pat. Nos. 4,992,000, 4,334,801, 4,400,115 and 5,659,983, dispersion of the fluidified material is contained by releasing it inside a protective hood over the bed of the body of water.
These known solutions are only partly successful in preventing dispersion, on account of the hood being moved parallel to the pipeline, so convection sustaining the inert material particles still persists in the areas from which the hood is removed.
Regardless of dispersion of the fluidified inert material, known solutions also fail to ensure even coverage of the pipeline.